Isn't "greatest bass player" an oxymoron?
A guitar teacher once said, "Look, you can't handle chords and you haven't learned the scales - play the bass."
(btw, John Kerry is a bass player)
Before Jaco, it might have been -- after Jaco, the bass was changed forever.
Search around the net and see if you can find a link to "Portrait of Tracy" -- Jaco playing all in one take. Or any of his work with the band Weather Report.
As far as (current) bass players in general, apparently you've never heard Victor Wooten's music?